Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$140.49	13.234%	$159.0824	$159.08	$159.10	$159.10
Purchase #2	$119.56	6.332%	$127.1305	$127.13	$127.15	$127.10
Purchase #3	$142.33	7.850%	$153.5029	$153.50	$153.50	$153.50
Purchase #4	$127.61	13.116%	$144.3473	$144.35	$144.35	$144.30
Purchase #5	$247.31	3.423%	$255.7754	$255.78	$255.80	$255.80
Purchase #6	$213.92	7.356%	$229.656	$229.66	$229.65	$229.70
Purchase #7	$200.59	3.812%	$208.2365	$208.24	$208.25	$208.20
7 purchase totals =	$1,191.81		$1,277.7310	$1,277.74	$1,277.80	$1,277.70